1. Field of the Invention
The present invention relates to a fluid-sealed anti-vibration device which is used in an engine mounting and the like.
2. Description of the Prior Art
A cone-shaped mounting is known in the prior art wherein a first connecting member secured to a vibration generating side, a second connecting member secured to a vibration receiving side, and a substantially cone-shaped elastic body member for connecting the first and second connecting members are provided, and provided inside the elastic body member is a fluid chamber, of which part of an elastic wall is the elastic body member and which is divided by a partition member into a main fluid chamber and a sub-fluid chamber, and a first orifice passage is provided for communicating with both fluid chambers.
Also, a cylindrical bushing is also known in the prior art wherein inner and outer cylindrical tubes are connected by an elastic member, a plurality of fluid chambers divided by the elastic member in the circumferential direction is provided, and an orifice passage is arranged to communicate with these fluid chambers.
As a cone-shaped mounting, a fluid sealed type anti-vibration rubber device which is provided with a partition member for dividing its inner part into a main fluid chamber and a sub-fluid chamber, a part of which is an elastic membrane which is deformed elastically with change in the internal pressure of the main fluid chamber and an orifice passage provided extending to the partition member for communication between the main fluid chamber and the sub-fluid chamber is known. In the mounting, a partition member comprises an elastic partition member which is integrally formed with an elastic membrane and an orifice portion formed around the elastic membrane and interposed between a first supporting member and a second supporting member, and a boundary portion of the elastic membrane and the orifice portion is clamped by the first supporting member and the second supporting member (see FIG. 4).
In the construction of the mounting, when a stepped portion is formed by projecting upward the central portion of the first supporting member positioned at a main fluid chamber side, a fluid mass section enclosed by this stepped portion is formed on the elastic membrane and the fluid mass section and the main fluid chamber communicate through an opening portion which is provided in this stepped portion, the elastic membrane is deformed elastically by the vibration input to the main chamber, fluid column resonance is generated in this fluid mass section and originating from this fluid column resonance, the maximum value (hereinafter called the peak) and the minimum value (hereinafter called the bottom) can be formed for a dynamic spring characteristic. Thereby, a low dynamic spring effect can be achieved in a wide frequency region.
Decrease in vibration based on flow of a fluid between fluid chambers in the cone-shaped mount is used to decrease the vibration, for example, in the vertical direction (hereinafter referred to as xe2x80x9cthe Z-axis directionxe2x80x9d) among vibrations in three axial directions consisting of X, Y, and Z axes at right angles to one another. and therefore the decrease in vibration does not affect the front and rear direction (hereinafter referred to as xe2x80x9cthe X-axis directionxe2x80x9d) and the right and left direction (hereinafter referred to as xe2x80x9cthe Y-axis directionxe2x80x9d).
In the case of the decrease in vibration based on liquid flow between the fluid chambers in the cylindrical bushing, when the axial direction of the cylindrical bushing is adjusted to the Z-axis direction, if four fluid chambers are formed at intervals of 90xc2x0 in the circumferential direction and each fluid chamber is arranged in the directions of the X and Y axes, vibrations in each of the X and Y-directions can be decreased by one cylindrical bushing, but the vibration in the Z-axis direction can not be decreased.
Accordingly, to decrease all vibrations in the directions of the three axes, X, Y, and Z, when for example, the cone-shaped mounting and the cylindrical bushing are combined, more than one fluid-sealed anti-vibration device must be provided. In this case, the number of devices becomes many and their arrangement is complicated, increasing the total weight and cost of the device. It is therefore an object of the present invention to decrease all vibrations in the directions of the three axes, X, Y, and Z by the vibration decrease, based on the liquid flow between the fluid chambers in one fluid-sealed anti-vibration device.
Also, in the construction of the cone-shaped mounting, a partition member comprises an elastic partition member interposed between a first supporting member and a second supporting member, a boundary portion of the elastic membrane and the orifice portion is clamped by the first and supporting member, and tension of the elastic member is decided by the clamping amount, that is, a clamping overlap width. Resonance frequency of the elastic membrane portion is decided by tension thereof.
If the resonance frequency of the elastic membrane portion can be tuned by controlling the clamping width, fluid column resonance in the fluid mass section can be freely tuned through optional tuning of the resonance frequency of the elastic membrane portion. However, the controlling of the clamping width feasible only in the direction which lowers its tension by reducing the clamping width. It is therefore desired to enlarge the tuning width, as it is relatively narrow.
Further, when the stepped portion projecting from the first supporting member into the main fluid chamber and a bevel member vibrating within the main fluid chamber in an integral manner with the elastic body member, it is necessary to secure a certain clearance h between the bevel member and the stepped portion. Therefore, the overall height of the engine mount becomes high and the size becomes large, correspondingly. It is therefore an object of the present invention to expand the tuning width of resonance frequency of the elastic membrane and realize an entire fluid sealed anti-vibration device compact in size.
The primary object of the present invention is to overcome the above-mentioned problems and to provide a fluid-sealed anti-vibration device comprising a cone-shaped mounting section and a cylindrical bushing section, wherein the cone-shaped mounting section comprises a first connecting member secured to a vibration generating side, a second connecting member secured to a vibration receiving side, a substantially cone-shaped elastic body member for connecting the first and second connecting members, a fluid chamber of which part of an elastic wall is the elastic body member and which is divided by a partition member into a main fluid chamber and a sub-fluid chamber, and a first orifice passage for communicating with the main and sub-fluid chambers, and the cylindrical bushing section comprises a plurality of side fluid chambers which are provided in a circumferential direction at a predetermined intervals on the outer circumference of the elastic body member and of which part of an elastic wall is the elastic body member, and a second orifice passage for communicating with each of the side fluid chambers, characterized in that the cylindrical bushing section and the cone-shaped mounting section are integrally provided.
According to a second object of the present invention, the cylindrical bushing section is provided with the side fluid chambers and open recess chambers which are alternately formed in the circumferential direction, and a bottom section of the recess chamber is a thin section of the elastic body member in the cone-shaped mounting section.
According to a third object of the present invention, the side fluid chambers are paired at intervals of 180xc2x0 in the circumferential direction, each of which is arranged in the front and rear direction of a car body.
According to a fourth object, the cone-shaped mounting section and the cylindrical bushing section use the first and second connecting members in common.
According to a fifth object, the partition member is provided as two overlapping members which are temporarily integrated by engaging a tapered hole formed on one of the two members with a tapered projection formed on the other.
According to a sixth object, a fluid sealed anti-vibration rubber device of this invention is provided with an elastic membrane which is deformed elastically with the change in the internal pressure of the main fluid chamber and which is provided as a part of the partition member, the partition member comprises an elastic partition member which forms a fluid mass concave section opening toward the main fluid chamber on the elastic membrane in one unit with a ring-shaped vertical wall portion enclosing the elastic membrane, and a first supporting member and a second supporting member, each of which has an open portion formed on the elastic membrane equivalent portions for clamping the elastic partition member from the front and back sides, and a projecting portion is provided at the portion contacting the ring-shaped vertical wall portion of the first supporting member, and the ring-shaped vertical wall portion is turned down in the central direction or in the opposite outward direction of the elastic membrane by this projecting portion.
The fluid-sealed anti-vibration device of the first object uses the elastic body member of the cone-shaped mounting section and the cylindrical bushing section is formed on the circumference of the elastic body member. In this manner, both functions of the conventional cone-shaped mounting and the cylindrical bushing can be displayed at the same time in spite of being a single device. For example, when a main vibration input direction of the cone-shaped mounting section is arranged to be the Z-axis direction and a main vibration input direction of the cylindrical bush section is arranged to be the X-axis direction, if a pair of side fluid chambers in the cylindrical bushing is also arranged in the X-axis direction, each vibration in the directions of the X and Z axes can be eliminated at the same time based on the liquid flow between the fluid chambers in a single device. Further, if a pair of fluid chambers in the cylindrical bushing is arranged in the Y-axis direction, it is possible to decrease the vibration based on the liquid flow between fluid chambers relative to vibration input from the Y-axis direction. It is also possible to reduce the vibrations based on the liquid flow between the fluid chambers relative to vibrations input from the directions of the X and Y axes if a pair of fluid chambers is arranged in the directions of the X and Y axes respectively.
The elastic body member is integrally provided so that it is used in common as an elastic wall forming each fluid chamber of the cone-shaped mounting section and the cylindrical bushing section. It is therefore possible to reduce the number of parts and to provide a compact and lightweight device. The number of anti-vibration devices to be used for obtaining the same effect can be reduced by half. It is therefore possible to simplify the arrangement and reduce the weight and cost.
The side fluid chamber of the cylindrical bushing section has a substantially triangle cross-section and the elastic body member of the cone-shaped mounting section is used as a part of the wall forming the side fluid chamber. Thus, when the cylindrical bushing section is formed on the periphery (circumference) of the cone-shaped mounting section, it is not necessary to increase each measurement of height and width in a single cone-shaped mounting section. Accordingly, because substantial installation space can be set to the same space as the case of a single cone-shaped mounting section, a remarkably compact body is realized.
According to the second object, because of the provision of the recess chamber and the thin section, the device can absorb a large input of vibration and improve the durability. Further, since the bottom section of the recess chamber in the cylindrical bushing section is provided with a thin section, a section of the recess chamber of the elastic body member surrounding the main fluid chamber of the cone-shaped mounting section becomes a thin section. If the thin section is set to resonate in a medium frequency range, membrane resonance is generated by input vibration in the medium frequency range to the device so as to realize a low dynamic spring effect in the medium frequency range of the cone-shape mounting section.
According to the third object, the main vibration input direction of the cone-shaped mounting section is arranged in the vertical direction of the car body, the main vibration input direction of the cylindrical bushing section is arranged in the longitudinal direction of the car body, and a pair of side fluid chambers in the cylindrical bushing section is arranged in the longitudinal direction of the car body, each vibration in the vertical direction and the longitudinal direction of the car body which is often required for the purpose of anti-vibration can be eliminated at the same time based on the liquid flow between the fluid chambers in the single device.
According to the fourth object, the first connecting member, the second connecting member, and the elastic body member can be used in common with the cone-shaped mounting section and the cylindrical bushing section. It is therefore possible to reduce the number of parts to simplify the construction, whereby the device can be lightened as a whole and a compact construction can be realized compared with the prior art in which separate anti-vibration devices had to be simply integrated. Further, it is possible to reduce the number of devices by half and the arrangement can be simplified compared with the case where the same effect is obtained in the prior art.
According to the fifth object, two members forming the partition member are temporarily integrated by engaging the tapered projection with the tapered hole. It is therefore possible to handle the partition member as a single integrated part during assembling and realize an easy assembly.
According to the sixth object, a ring-shaped vertical wall portion enclosing an elastic membrane is formed on an elastic partition member and when this ring shape vertical wall portion is clamped by first and second supporting members, a clamping overlap width becomes large. Furthermore, when the ring-shaped vertical wall portion is turned down in the central direction of the elastic membrane by the projecting portion which is formed on the first supporting member, it is possible to lower the tension of the elastic membrane, and when the ring-shaped vertical wall portion is turned outward (the opposite direction to the central direction), the tension of the elastic membrane can be raised. Thus, when the tension is raised, the resonance frequency of the elastic membrane can be raised and when the tension is lowered, the resonance frequency can be lowered. So, it becomes possible to raise and lower the resonance frequency of the elastic membrane by changing its tension. As a result, the tuning width of fluid column resonance in the fluid massed concave portion can be expanded.
Furthermore, because the fluid massed concave portion is provided in the elastic partition member, the first supporting member can be made in a flat shape. As a result, it is not necessary to project the central portion into the main fluid chamber and it becomes possible to make the entire fluid sealed anti-vibration rubber device in a compact size accordingly.